We will continue our studies in several directions. We wish to identify the peptides to which NEM and oxidized glutathione bind when they inhibit tubulin polymerization. Are these the same peptides to which MAP2 and tau bind when they are cross-linked to tubulin by diamide? If there is a unique peptide in tubulin such that blockade of its sulfhydryls or cross-linking of them with diamide inhibits tubulin polymerization, we wish to know its sequence. We will continue our studies of NEM activation of eggs in two directions. The first is the attempt to identify the site of NEM action in the egg surface. The second is whether NEM acts by means of liberation of calcium from a cytoplasmic store. In addition, we will follow the formation of coated pits which form after NEM activation and which we now find form during all types of egg activation. We will trace the formation of these pits during the mitotic cycle and explore the ultimate site of horse radish peroxidase which is taken up by these structures. We will continue studies of the membrane bound Ca ion2 ATP-ase of sea urchin eggs which is reversibly inhibited by diamide oxidation of its sulfhydryls.